What is the van Deemter equation, and how can it be used to
improve a separation?...
What is the van Deemter equation, and how can it be used to
improve a separation? Support your answer with a sketch of a
typical van Deemter plot, making sure to label your axes.
Solutions
Expert Solution
Van Deemter equation gives an
optimum velocity where the separation efficiency is the maximum and
thus it is used to improve a separation. The equation and the
typical Van Deemter plot is given in the attached images.
Derive an expression of the van Deemter equation that shows how
to calculate the minimum value of H based upon the values for A, B
and C and not flow rate. (Assume the C terms are combined into one
C term).
Van Deemter equation is written as: H = A + B/u + Cu where u is
mobile phase linear velocity. Sketch a typical van Deemter plot to
show how H depends on u, and briefly explain each term in the
equation and sketch how each depends on u.
Which term in the Van Deemter equation is affected by the
following changes and would plate height increase or decrease?
Explain your reasoning.
(a) Changing the mobile phase from a gas to a supercritical
fluid
(b) Changing the stationary phase thickness in a wall coated
open tubular GC column from 5µm to 0.5µm.
Consider an HPLC analysis. Which term in the van Deemter
equation plays a minimal role in
determining the theoretical plate height (H)? Justify your
answer.
Consider a capillary column GC experiment. Which term in the van
Deemter equation is most
strongly affected by increasing the inner diameter of the column?
Justify your answer.
How can the Van Der Waals equation of state be used to determine
whether a substance will be a solid, liquid or gas at a certain
temperature and pressure?
For Van Der Waals equation
(P + a/V2)(V - b) =
nRT
How can you find the values of
"a" and "b" using an experiment? Please explain the method of the
experiment too
Describe how ratio analysis can be used to improve operations
and reduce debt ?
Describe how identifying trends and patterns in financial
statements over reporting periods can yield insights into the
client’s business ?